Outdoor decks or patios are often aligned vertically on the exterior of buildings (for example, apartment buildings) such that the deck of a lower unit is disposed below that of an upper unit. These outdoor decks are typically made of planks that span a number of joist members. When it rains, water falls through the planks of the deck and onto any decks located below. Thus, stacked exterior decks may not be desirable or useful during rainy conditions. Additionally, debris such as dirt, spilled food or beverages, or other items can fall through the planks from an upper deck to a lower deck and onto the occupants thereof. One solution is to attach waterproof sheathing material on the undersides of the joists to collect and redirect water and debris. This sheathing, however, is unsightly and can lower the perceived or actual clearance between the lower decks. Additionally, if the sheathing is not pitched properly, water may pool thereon. This pooling may lead to sheathing or joist degradation and rotting.